pv

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Text.RegularExpressions;

namespace PHPVariables
{
    class PHPVariables
    {
        static void Main(string[] args)
        {
            HashSet<string> variables = new HashSet<string>();
            StringBuilder line = new StringBuilder(Console.ReadLine());
            string commentPattern = @"([/]{1}[*]{1}.*[*]{1}[/]{1})|([/][/].*)|([#]{1}.*)|(?<multiLineComment>([/]{1}[*]{1}.*))";
            string varPattern = @"([^\\]|[\\]{2})[$]{1}(?<var>[A-Za-z0-9_]+)";
            bool multiLineComment = false;
            while (line.ToString()!="?>")
            {
                line.Insert(0, ' ');
                if (multiLineComment)
                {
                    if (line[line.Length-1]=='/' && line[line.Length-2] == '*')
                    {
                        multiLineComment = false;
                    }
                    line = new StringBuilder(" ");
                }
                Match match = Regex.Match(line.ToString(), commentPattern);
                while (match.Success)
                {
                    if (match.Groups["multiLineComment"].Success)
                    {
                        multiLineComment = true;
                    }
                    line.Replace(match.ToString(), "");
                    match = match.NextMatch();
                }
                Match m = Regex.Match(line.ToString(), varPattern);
                while (m.Success)
                {
                    variables.Add(m.Groups["var"].ToString());
                    m = m.NextMatch();
                }
                line = new StringBuilder(Console.ReadLine());
            }
            List<string> list = new List<string>();
            Console.WriteLine(variables.Count);
            foreach (var item in variables)
            {
                list.Add(item);
            }
            string[] arr = list.ToArray();
            Array.Sort(arr);
            for (int i = 0; i < arr.Length; i++)
            {
                Console.WriteLine(arr[i]);
            }
        }
    }
}